New UL rules

Maybe we should retire. I just did, at least for 1-1/2 days and it feels great. Brewed a Cream Ale with honey, a Belgian Tripel and a Pale Ale.

I just design my stuff to UL60601 or RTCA/DO-160 or whatever otehr stadard is required and then it gets sent to a test house to inspect the design and test.

IME, if one does a reasonable design with a good gut feel for what is safe it passes.

To me it was explained as Chinese Engineering.

Not all of us are old and tired like that. ;) (Even though you get probably 2 orders of magnitude more exercise than I do). I doubt I'll ever retire, as long as my health holds up and business keeps coming in.

Cheers

Phil Hobbs

AFAIR:

It?s 42V DC for UL, 24V DC for IEC for SELV, depending on what stan dards you have to comply to

If you have more than 15W available, then there is the risk of fire, so you need glowwire tests etc for IEC, for UL you need approved materials for fi re (UL recognized and approved components)

It makes sense for once, ELV won?t kill you by electric shock, but if the current is high enough you can have a fire hazard in connections

Remember the voltage is including transients, so a power supply with oversw ing must have lower than 24V nominal voltage

Lastly, clearances below 0.2mm constitutes risk of short, so you need a DFM EA or tests to show no hazard is developed even by a short in low voltage c ircuits

Cheers

Klaus

Did yo' mama teach you to be snotty like that? ;)

I sort of doubt that you were ever 17, or, if you were, you were quite as all-wise as you let on.

But I could be wrong.

Cheers

Phil Hobbs

SELV no longer exists at all, or so I gather.

Cheers

Phil Hobbs

I'm not planning to certify it myself, because I'm not the one selling the actual product--it's a licensing thing. I just want to make sure it'll pass the new IECxxxx regs-of-the-month without being tooooo too paranoid.

Cheers

Phil Hobbs

I like building stuff, I mostly hope I can find someone to keep paying me. The most fun is building something new (to you.)

George H.

We are getting ready to UL certify one of our battery products: A UPS-type device for variable voltage (up to 70 VDC), with some unique low-voltage te lemetry, and power-limited, life-safety stuff. (You may recall I asked abo ut fishpaper a while back.. Bingo.) :)

Anyway, I'm expecting a super-huge hassle. So much in fact, that I've purposely designed-in a couple distracting/entic ing Easter-Eggs to give the UL evaluation team something to focus on.

The rational thing to do of course is to involve UL very early in the desig n. For lots of (usually bad) reasons, I won't go into why that wasn't done in this case.

Our product touches about 30 different UL Standards (some quite tangentiall y), and most of them are avoided by using parts that are already UL tested.

The two things I'm "worried" about the most, is UL not allowing the 120 VAC and power-limited stuff to reside on the same PCB. (?) And then, the cust om enclosure design itself. ..."Articulated finger" stuff, and all that.

It "should" pass (with hopefully only moderate effort), but I'm guessing I' m not that lucky.

I've seen lawyers do that in intellectual property litigation, to get the other guys to shoot all their bullets at non-vital targets. Like giving liver to the guard dogs. ;)

I'd be interested to hear the play-by-play. It'll be a good way for you to blow off steam, too. ;)

Cheers

Phil Hobbs

When I joined the Air Force, I was assigned to the Officer's building where I swept the halls. An old Sergeant Major asked me a few questions, then asked me to take a few exams. I wrote off the entire Electronics course and got the second highest mark ever achieved in the school. The highest mark was gained by a candidate with a masters degree in engineering.

The next challenge was to dismantle a 5-tube superhet, draw the schematic, and put it back together. I had it completely disassembed by noon, and completely reassembled, tuned, and working by 5:00 pm.

They then asked me to completely rewrite the exams for the entire cirriculum, and then made me an instructor. All my students passed.

After a few postings, I was sent to France with NATO. I had a number of jobs simultaneously, then was asked to generate a training course for Sergeants and Warrant Officers to pass their Level 4 Trade Board exams.

I was a mere Corporal at the time.

Most of them passed. This had a significant effect on their pensions when they left the Air Force. I have always felt bad about the ones who failed.

You seem to have an unusual need to attack me whenever I post. You have called me a liar, made a number of insulting posts to me, and behaved as you never do with anyone else.

If it makes you feel good, do as you wish. There is nothing you can do to make me feel bad, except you lower yourself. I don't know why.

When did I call you a liar?

I do think you're a bit of an arrogant prat, but that doesn't make you that unusual in SED. ;)

Cheers

Phil Hobbs

Hmmmm... one joule can be rather damaging...

IEC defines ELV to be less than 50 Vac or 120 Vdc. Most standards seem to agree on 50 Vac, but some put the DC limit at 60 V, 75 V or 120 V.

SELV (Separated Extra-Low Voltage) essentially requires a _floating_ ELV circuit, such as an inoculation transformer (or floating battery) feeding a _single_ load.

Some time ago.

Maybe you are reading too much from the tone of my posts. As you recall. I have serious mold headaches. It is very difficult to sound cheerful when your head is splitting. The symptoms are debilitating and permanent. There is no cure.

I do my best to sound civil, but when you are in pain, the range of words you have available are different and much more limited than when you are free of pain. Because it is so costly to try to find words, I try to keep my posts on topic and avoid the trivial, off-topic posts that are so popular with some.

I had a UL inspector tell me I could not use a LED because anything over .25 volts had to have a .35 inch spacing.

Awsome. How did you get around it?

I won't ever fully retire either because I need the challenge. However, I am throttling back and trying to only take really tough cases. Projects where a team is about to throw in the towel but the boss wants the product.

It's not about being old or tired. I feel that at some point volunteering should become more important in my life especially in fields where many others won't go, like Alzheimer's care homes. The other reason is that as we age excercise becomes ever more important. Preferably I don't want to be shuffling around with a walker 20 years from now.

On Jun 2, 2018, Neon John wrote (in article):

Bingo! When I write requirements for electrical safety, I never say ?UL?, because there are better choices.

I instead say ?NRTL? (Nationally Recognized Testing Lab). This allows people to compare and choose the best lab for them. UL never wins.

Joe Gwinn

I looked, and didn't see anything like that. We did have a bit of a dust-up about PLLs a month or two back, but AFAICT nothing personal. Maybe you're confusing me with someone else?

You certainly aren't the worst offender--your stuff is often useful and encouraging--but ISTM that sometimes you don't distinguish clearly between an argument and a quarrel.

I'll try to bear in mind your difficulty and make suitable allowances.

Feel better!

Cheers

Phil Hobbs